1. Field
The present disclosure relates to a fuel cell.
2. Description of the Related Art
In general, a solid polymer electrolyte fuel cell includes a solid polymer electrolyte membrane, which is a polymer ion-exchange membrane. The fuel cell includes a membrane electrode assembly (MEA), in which an anode electrode is disposed on one surface of the solid polymer electrolyte membrane and a cathode electrode is disposed on the other surface of the solid polymer electrolyte membrane. The anode electrode and the cathode electrode each include a catalyst layer (electrode catalyst layer) and a gas diffusion layer (porous carbon).
The membrane electrode assembly and separators (bipolar plates) that sandwich the membrane electrode assembly constitute a power generation cell (unit fuel cell). A predetermined number of power generation cells are stacked and used, for example, as a vehicle fuel cell stack.
In some fuel cells, metal separators having thin plate-like shapes are used. On a surface of one of the metal separators facing the anode electrode, a plurality of wave-shaped fuel gas channels (reactant gas channels), which are wave-shaped in plan view, are formed. A fuel gas flows through the fuel gas channels along an electrode surface of the anode electrode. On a surface of one of the metal separators facing the cathode electrode, a plurality of wave-shaped oxidant gas channels (reactant gas channels), which are wave-shaped in plan view, are formed. An oxidant gas flows through the oxidant gas channels along an electrode surface of the cathode electrode.
A coolant channel is formed between the back side of the wave-shaped fuel gas channels of one of the separators and the back side of the wave-shaped oxidant gas channels of an adjacent separator. A coolant flows through the coolant channel in a direction along the electrode surfaces.
When the fuel cell is a so-called “internal-manifold fuel cell”, a reactant gas manifold, through which a reactant gas flows, and a coolant manifold, through which a coolant flows, are formed so as to extend through the power generation cell in the stacking direction. In this case, because the reactant gas manifold has a comparatively small opening area, in order to uniformly and reliably supply the reactant gas to an electrode reaction surface, a buffer portion, which includes a plurality of embossed portion or guide portions, is formed between the reactant gas manifold and the reactant gas channel. For example, Japanese Unexamined Patent Application Publication No. 2014-137937 describes a fuel cell stack utilizing such technology.